Designation G158 − 98 (Reapproved 2016) Standard Guide for Three Methods of Assessing Buried Steel Tanks1 This standard is issued under the fixed designation G158; the number immediately following the[.]
Trang 1Designation: G158−98 (Reapproved 2016)
Standard Guide for
This standard is issued under the fixed designation G158; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last reapproval A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The purpose of this guide is to provide three methods of inspecting and assessing buried steel tank(s) for corrosion damage and determining the suitability of these tanks prior to application of
cathodic protection
1 Scope
1.1 This guide covers procedures to be implemented prior to
the application of cathodic protection for evaluating the
suit-ability of a tank for upgrading by cathodic protection alone
1.2 Three procedures are described and identified as
Meth-ods A, B, and C
1.2.1 Method A—Noninvasive with primary emphasis on
statistical and electrochemical analysis of external site
envi-ronment corrosion data
1.2.2 Method B—Invasive ultrasonic thickness testing with
external corrosion evaluation
1.2.3 Method C—Invasive permanently recorded visual
in-spection and evaluation including external corrosion
assess-ment
1.3 This guide presents the methodology and the procedures
utilizing site and tank specific data for determining a tank’s
condition and the suitability for such tanks to be upgraded with
cathodic protection
1.4 The tank’s condition shall be assessed using Method A,
B, or C Prior to assessing the tank, a preliminary site survey
shall be performed pursuant to Section8and the tank shall be
tightness tested pursuant to5.2to establish that the tank is not
leaking
1.5 While this guide provides minimum procedures for
assessing a tank’s condition, this guide does not provide
minimum installation procedures or requirements for upgrades
of the tank by cathodic protection
1.6 The values stated in inch-pound units are to be regarded
as standard The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
2 Referenced Documents
2.1 The most recent version of the following documents should be consulted as references by those using this guide:
2.2 ASTM Standards:2
D2216Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
E114Practice for Ultrasonic Pulse-Echo Straight-Beam Contact Testing
E797Practice for Measuring Thickness by Manual Ultra-sonic Pulse-Echo Contact Method
E1323Guide for Evaluating Laboratory Measurement Prac-tices and the Statistical Analysis of the Resulting Data
E1526Practice for Evaluating the Performance of Release Detection Systems for Underground Storage Tank Sys-tems(Withdrawn 2002)3
G51Test Method for Measuring pH of Soil for Use in Corrosion Testing
G57Test Method for Field Measurement of Soil Resistivity Using the Wenner Four-Electrode Method
1 This guide is under the jurisdiction of ASTM Committee G01 on Corrosion of
Metals and is the direct responsibility of Subcommittee G01.10 on Corrosion in
Soils.
Current edition approved May 1, 2016 Published May 2016 Originally
approved in 1998 Last previous edition approved in 2010 as G158 – 98 (2010).
DOI: 10.1520/G0158-98R16.
2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 United States
Trang 22.3 ASNT Standard:4
ASNT SNT-TC-1APersonnel Qualification and
Certifica-tion in Nondestructive Testing
2.4 NACE International Standards:5
RP-0169Standard Recommended Practice-Control on
Ex-ternal Corrosion on Underground or Submerged Metallic
Piping Systems
RP-0187Standard Recommended Practice-Design
Consid-erations for Corrosion Control of Reinforcing Steel in
Concrete
RP-0285 Standard Recommended Practice-Corrosion
Con-trol of Underground Storage Tank Systems by Cathodic
Protection
2.5 Environmental Protection Agency Methods:6
EPA SW 846Test Methods for Evaluating Solid Waste
EPA 371.1Measurement of Sulfate Reducing Bacteria
2.6 National Fire Protection Association (NFPA)7
NFPA 329Recommended Practice for Handling
Under-ground Releases of Flammable and Combustible Liquids
2.7 Underwriters Laboratories Inc.8
UL 58Steel Underground Tanks for Flammable and
Com-bustible Liquids
3 Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 buried—to be placed in the ground and covered with
earth
3.1.2 cathodic protection—an applied technique to prevent
further corrosion of a metal surface by making that surface the
cathode of an electrochemical cell For example, a tank system
can be cathodically protected through the application of either
galvanic anodes or impressed current
3.1.3 corrosion specialist/cathodic protection specialist—a
competent person who by reason of knowledge of the physical
sciences and the principles of engineering and mathematics,
acquired by education and related practical experience, is
qualified to engage in the practice of corrosion control on
buried or submerged metallic piping systems and metallic
tanks Such persons shall be registered professional engineers
or persons recognized as corrosion specialists or cathodic
protection specialists by NACE, if their professional activities
include suitable experiences in external corrosion control on
buried or submerged metallic piping and tanks
3.1.4 corrosion technician—a person possessing basic
knowledge of corrosion and corrosion control, who is capable
of performing routine, well defined work under the supervision
of the corrosion specialist/cathodic protection specialist
3.1.5 invasive procedure—a method of determining the
corrosion status of a tank by assessing the tank from the inside
as part of the upgrade procedure Further, for the purposes of this guide, it does not require manned entry into the tank (See
non-invasive.) 3.1.6 limitations—The user of this guide is encouraged to
review any available third party verification information pro-vided as part of the vendor selection process
3.1.7 noninvasive procedure—a method of determining the
corrosion status of a tank from the characteristics of its surroundings with minimal entry into the tank Further, for the purposes of this guide, it does not require manned entry into
the tank (See invasive.) 3.1.8 pH—the numerical value of the negative logarithm of
the hydrogen ion concentration in moles per litre in an electrolyte
3.1.9 redox potential—potential of platinized platinum
elec-trode in a redox environment (reversible system) The value of redox potential depends on whether the system is in the oxidized, partially oxidized, partially reduced, or reduced state
3.1.10 tank tightness test—a method capable of detecting a
0.1 gal/h leak rate, while accounting for any applicable effects
of thermal expansion or contraction of the product, of vapor pockets, of tank deformation, of evaporation or condensation, and of the location of the water table The method must be capable of detecting a 0.1 gal/h leak rate with a probability of detection of at least 0.95 and a probability of false alarm of at most 0.05 or in accordance with NFPA 329
3.1.11 unconditional probability of corrosion failure—the
probability of corrosion failure which includes a determination
of whether localized, pitting, or general corrosion is occurring
3.1.12 underground storage tank (UST)—any one or
com-bination of tanks (including connected underground piping), the volume of which is 10 % or more beneath the surface of the ground
3.1.13 upgrade—the addition to or retrofit of UST systems
using approaches including, but not limited to, cathodic pro-tection to improve the ability of a UST system to prevent a release
3.1.14 UST—see underground storage tank (see3.1.12)
3.1.15 vendor provided information—The user is referred to
Annex A1for a specific form and format of information which must be provided by a vendor This information consists of historic performance data on a method and is mandated as part
of the guide
4 Significance and Use
4.1 This guide provides three methods for determining the suitability of a buried steel tank to be upgraded with cathodic protection
4.2 This guide may be used to assess any UST, including non-regulated USTs
4.3 This guide provides three alternative methods but does not recommend any specific method or application The responsibility for selection of a method rests with the user
4 Available from The American Society for Nondestructive Testing (ASNT), P.O.
Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.
5 Available from National Association of Corrosion Engineers (NACE), 1440
South Creek Dr., Houston, TX 77084-4906.
6 Available from US Environmental Protection Agency, Office of Underground
Storage Tanks, 401 “M” St SW, Washington, DC 20460.
7 Available from Underwriters Laboratories (UL), Corporate Progress, 333
Pfingsten Rd., Northbrook, IL 60062.
8 Available from National Fire Protection Association (NFPA), 1 Batterymarch
Park, Quincy, MA 02269-9101.
Trang 34.4 This guide has specific requirements for vendor
pro-vided information which should be requested and reviewed by
the user
5 Permits, Plans and Tank Leak Testing
5.1 Prior to engaging in any activities relating to the
alteration, repair, or upgrade of any UST system, consult all
necessary authorities to obtain any required permits
5.2 Tank Leak Testing:
5.2.1 To establish that tanks are not leaking prior to
assessment, they shall be assessed by a leak detection system
This leak detection assessment alone is not sufficient to
determine that a tank is suitable for upgrading with cathodic
protection under this guide
5.2.2 A tightness test or another release detection system in
accordance with NFPA 329 shall be used Any release detection
must be capable of detecting a leak from any portion of the
tank that routinely contains product, and be independently
evaluated and certified in accordance with PracticeE1526 or
the equivalent Leak detection results shall be provided to the
corrosion specialist/cathodic protection specialist
5.2.3 This testing shall be accomplished within six months
prior to performing any of the assessment procedures
6 Required Approvals and Certifications
6.1 The corrosion assessment work carried out under this
guide shall be performed under the responsible direction of a
corrosion specialist/cathodic protection specialist as defined in
3.1.3
6.2 The corrosion specialist/cathodic protection specialist
shall certify to the tank owner or operator that the personnel
performing the assessment work on the tank are knowledgeable
of all the applicable procedures in this guide
6.3 The corrosion specialist/cathodic protection specialist
shall certify to the tank owner or operator that all work was
performed in strict accordance with this guide
7 General Safety Requirements
7.1 All personnel shall comply with applicable federal,
state, and local health and safety codes and regulations
8 Preliminary Site Survey
8.1 A corrosion technician, under the responsible direction
of the corrosion specialist/cathodic protection specialist, shall
obtain tank site specific information as appropriate to the
method of assessment to be used
8.1.1 Facility Information:
8.1.1.1 Address or location, and
8.1.1.2 Name and telephone number of owner and operator
contact personnel
8.1.2 Tank and Piping Details:
8.1.2.1 Number and capacity,
8.1.2.2 Location and dimensions,
8.1.2.3 Age,
8.1.2.4 Material of construction,
8.1.2.5 Electrical isolation,
8.1.2.6 Type of product stored,
8.1.2.7 Names of site contact personnel, 8.1.2.8 Backfill material,
8.1.2.9 Coatings and linings, 8.1.2.10 Leak history, 8.1.2.11 Repair history, 8.1.2.12 Site plans, 8.1.2.13 Installation specifications, 8.1.2.14 Tank excavation liners, and 8.1.2.15 As-built drawings
8.1.3 Information Not in the Immediate Vicinity of the Tanks—The presence of the following items, that are external
to the tank area, shall be investigated and included as appro-priate to the method of assessment of the suitability of tanks for upgrading with cathodic protection:
8.1.3.1 Stray dc current sources, 8.1.3.2 Existing cathodic protection systems, 8.1.3.3 Steel product and vent piping and fittings, and 8.1.3.4 Adjacent subsurface metallic/steel-reinforced con-crete structures
8.2 Preliminary Evaluation—Prior to assessing the tank, a
preliminary site survey must be performed pursuant to Section
8 and a tightness test must be performed pursuant to 5.2 to establish that the tank is not leaking
9 Method A—Noninvasive with Primary Emphasis on Statistical and Electrochemical Analysis of External Site Environment Corrosion Data ( 1 , 2 )
9.1 Field and Laboratory Testing—Noninvasive with Pri-mary Emphasis on Statistical and Electrochemical Analysis of External Site Environment Corrosion Data.
9.1.1 Tests shall be conducted by, or as directed by a corrosion specialist/cathodic protection specialist
9.1.2 Field Testing Procedures—Tests to be performed shall
include, but are not limited to, the following:
9.1.2.1 Stray Currents—Perform tests to detect the presence
of stray currents at each tank site This test shall consist of measuring structure-to-soil potentials at right angles at a minimum of two locations within the tank facilities and observing the measurements for not less than 2 h at a time when such influences are most likely to occur The monitor shall consist of a field data acquisition unit, with a minimum of 10-MΩ input impedance, used in conjunction with a stable reference cell(s) placed in contact with the soil in the vicinity
of the tank The instrument shall measure and store structure-to-electrolyte potential (voltage) data at least every 5 s through-out the entire duration of field investigation at the site or for 2
h, whichever is greater If variations of 650 mV or greater are measured during the test period, make 24-h recording measure-ments to confirm stray current effects
9.1.2.2 Tank Information:
(a) Locate all tanks and confirm materials of construction,
age, capacity, and dimensions Produce detailed site sketches describing the layout of the UST system and above grade pertinent details for each site
(b) Determine the presence and extent of internal corrosion
immediately below the fill riser If the depth of corrosion
Trang 4penetration in the tank shell exceeds 50 % of the tank wall
thickness, the UST shall be declared to have failed the test and
the procedure
(c) Determine if the tanks and piping are electrically
continuous
9.1.2.3 Bore Hole Tests:
(a) Determine locations for soil borings in the field Make
two test holes for each tank excavation zone with four or fewer
tanks For tank excavation zones with more than four tanks,
make one additional bore hole for each two additional tanks, or
part thereof Make the tank bore holes at opposite diagonal
ends of the tank excavation zone The tank excavation zone
shall be considered to extend no farther than 4 ft from the
nearest tank Complete the holes to the bottom of the deepest
tank
(b) In each tank bore hole, record measurements as the
boring progresses At 2-ft (0.6-m) intervals, make the
follow-ing tests:
(1) Measure the soil resistivity using the Wenner four pin
method in accordance with Test Methods G57
(2) Make structure-to-soil potential measurements in each
bore hole using a minimum 10-MΩ input impedance digital
voltmeter and a calibrated copper-copper sulfate reference
electrode sensing tip in direct contact with the soil in the bore
hole
(c) Measure the depth of observed, perched, or static water
table in each bore hole, if encountered
(d) In accordance with industry practices, gather one soil
sample each at the top, mid depth, and bottom of each hole
using either a split spoon or core sampling tube and place, seal,
and preserve the soil samples in containers for laboratory
analysis
(e) Backfill each hole and seal with a concrete or asphalt
plug
9.1.2.4 Other Field Considerations—The corrosion
specialist/cathodic protection specialist may also consider, but
not be limited to, performing and evaluating the following
tests:
(a) Current requirement,
(b) Coating resistance, and
(c) Coating efficiency.
9.1.3 Laboratory Testing Procedures—Send soil samples
collected at each site to a qualified soil laboratory where they
shall be tested in accordance with EPA SW 846 GuideE1323,
or other recognized industry test methods The report shall
include the results of all test methods used in the evaluation At
a minimum, obtain the following data:
9.1.3.1 Soil resistivity/conductivity,
9.1.3.2 Moisture content,
9.1.3.3 Soil pH,
9.1.3.4 Soluble chloride ion concentration, and
9.1.3.5 Sulfide ion concentration
9.1.4 The corrosion specialist/cathodic protection specialist
shall also consider, but not be limited to, performing and
evaluating the following tests The report shall include all test
methods used in the evaluation:
9.1.4.1 Redox potential, and
9.1.4.2 Sulfate ion concentration
9.1.4.3 Any other tests required by the external corrosion rate analysis model
9.1.5 Quality Control—One soil sample of every ten
samples analyzed shall be subjected to an independent quality control analysis of all data gathered in9.1.3 If the results of the quality control analysis fail to agree with the original analysis (within limits of experimental accuracy), reanalyze all samples collected since the last successful quality control analysis
9.2 Analysis and Determination of Suitability of a Tank for Upgrading with Cathodic Protection-Noninvasive with Pri-mary Emphasis on Statistical Analysis of External Site Envi-ronment Corrosion Data.
9.2.1 Basis for Analysis—By examining the environment in
the specific vicinity of the tank, a relationship between the aggressiveness of the environment and the rate of corrosion can
be statistically established Base the statistical analysis model used on a sufficient size data base with various factors that are accounted for statistically to reach a confidence level of 0.99 This will achieve consistency and reliability of the results One general form of the multivariate, non-linear regression analysis, which contains the minimum essential variables, is as follows:
E~Age!5 f~R, M, Cl, pH, S, SC, TS, P! (1)
where:
E (Age) = unconditional predicted age to corrosion failure,
Cl = chloride ion concentration,
S = sulfide ion concentration,
SC = stray current magnitude,
TS = tank size, and
P = tank structure to soil potential
9.2.2 Criteria of Acceptance for Upgrading With Cathodic Protection (using RP-0169, RP-0187, and RP-0285)—To be
acceptable as a means of determining the condition of tanks and their suitability for upgrading with cathodic protection, the procedure used shall, at a minimum, meet the following criteria:
9.2.2.1 The procedure shall be based on an evaluation of all
data gathered in situ in each bore hole together with all soil
sample data and the stray dc earth current monitor measure-ments taken at each site
9.2.2.2 The mathematical formulation of the procedure shall conform to accepted physical and electrochemical characteris-tics of the tank corrosion process Independent professional validation of these processes shall be done by an individual or individuals with experience in the relevant scientific or engi-neering disciplines
9.2.2.3 Parameter estimates shall be based on data derived from at least 100 sites where a minimum of 200 tanks were excavated, fully exposed, and evaluated by a qualified corro-sion specialist/cathodic protection specialist Maximum likeli-hood estimation or another procedure that meets the standards
of statistical or electrochemical admissibility shall be required
Trang 5Data used in estimation shall contain representative samples of
leaking and non-leaking tanks
9.2.2.4 Models proposed shall be specific as to soil type and
incorporate depth of ground water and rainfall experienced in
the immediate geographical area where testing takes place
9.2.2.5 The standard deviation of the predicted time to
corrosion failure shall not exceed 1.5 years The model shall
generate an unconditional probability of corrosion failure
based upon a comparison of actual tank age to its expected
leak-free life
9.2.3 Report Including Results, Analysis, and
Recommendations—The corrosion specialist/cathodic
protec-tion specialist shall prepare a report including results, analysis,
and recommendations as follows:
9.2.3.1 Base the report conclusions on the expected
leak-free life of a tank at a specific site as determined by the analysis
of the data necessary to determine which tanks are suitable for
upgrading with cathodic protection
9.2.3.2 The report shall provide the expected leak-free life
and present and future probabilities of corrosion failure for all
tanks investigated
9.2.3.3 The report shall include a listing of tanks whose age
is less than the expected leak-free life and for those tanks
where the probability of corrosion perforation is less than 0.05
9.3 Cathodic protection can be applied to those tanks that
have been tested in accordance with Sections8and9and meet
the following criteria:
9.3.1 The tank is confirmed to be leak free in accordance
with5.2
9.3.2 The tank age is less than the expected leak-free life
9.3.3 The probability of corrosion perforation of the tank is
less than 0.05
9.3.4 Either a tank tightness test is conducted between three
and six months after the tank is cathodically protected, or
monthly monitoring with another leak detection system is
implemented within one month after the addition of cathodic
protection Any leak detection system must meet5.2.2
9.4 A form is included inAnnex A1which must be utilized
to report the results of the authenticated vendor provided
information A research report containing examples of actual
authenticated vendor provided information is filed and
avail-able from ASTM.9
10 Method B—Invasive Ultrasonic Thickness Testing
with External Corrosion Evaluation
10.1 Field and Laboratory Testing—Invasive Ultrasonic
Thickness Testing with External Corrosion Evaluation:
10.1.1 Conduct the following procedures when assessing
the suitability of a steel tank for upgrading with cathodic
protection using an invasive method
10.1.2 Conduct tests by, or as directed by, the corrosion
specialist/cathodic protection specialist
10.1.3 Before a tank is suitable for upgrading with cathodic
protection using an invasive approach, the following
site-specific tests shall be conducted for each tank excavation zone
in accordance with industry recognized standard practices: 10.1.3.1 Perform the tests described in9.1.2.1
10.1.3.2 Soil resistivity in accordance with Test Methods
G57 These values shall be measured in the immediate vicinity
of the tank excavation zone and shall, as a minimum, be measured at depths of 5, 71⁄2, 10, 121⁄2, and 15 ft (1.5, 2.3, 3.5, and 5 m)
10.1.3.3 Structure to soil potential in accordance with NACE RP-0285 with at least five such measurements spaced uniformly about each tank excavation zone
10.1.3.4 Soil pH in accordance with Test MethodsG51, soil chlorides and sulfides in accordance with EPA SW 846 uniformly gathered from three locations about each tank excavation zone
10.1.3.5 Electrical continuity/isolation in accordance with NACE RP-0285 of each UST being evaluated
10.1.4 The corrosion specialist/cathodic protection special-ist should also consider, but not be limited to, performing and evaluating the following tests:
10.1.4.1 Redox potential, 10.1.4.2 Current requirement, 10.1.4.3 Coating resistance, 10.1.4.4 Coating efficiency, 10.1.4.5 Wall thickness
10.1.4.6 Soluble chloride ion concentration, 10.1.4.7 Sulfide ion concentration,
10.1.4.8 Sulfate ion concentration, and 10.1.4.9 Any other tests deemed necessary
10.2 Invasive Ultrasonic Thickness Testing with External Corrosion Evaluation:
10.2.1 This subsection provides the general procedure for assessing tanks prior to upgrading with cathodic protection through the use of invasive ultrasonic thickness testing in combination with the leak detection testing in accordance with
5.2and external corrosion evaluation procedures contained in
10.1 This procedure may be conducted using either manually manipulated or computer controlled remote controlled (ro-botic) ultrasonic sensor placement, control and measurement devices which do not require manned entry into the UST
10.2.2 Certification—Corrosion technicians performing
in-vasive ultrasonic thickness testing shall also be certified in accordance with ASNT recommended practice SNT-TC-1A and qualified under similar written practice with the equipment and procedures to be employed
10.2.3 Surface Preparation—In accordance with Practice
E114, the interior surface of the tank to be examined shall be uniform and free of loose scale, loose paint, dirt, or other deposits that affect examination If any such loose scale, loose paint, dirt, or other deposits exist which would prevent accurate ultrasonic thickness measurement of the remaining steel wall, they shall be removed prior to performing these measurements Tightly adhering paint, scale, or bonded coatings do not need to
be removed if they present uniform attenuation characteristics
10.2.4 Calibration—Calibrate the thickness measurement
sensor in accordance with PracticeE797
10.2.5 Couplant—Any couplant used shall be the stored
product or a material compatible with the stored product and
9 Supporting data have been filed at ASTM International Headquarters and may
be obtained by requesting Research Report RR:G01-1019.
Trang 6shall be appropriate for the surface finish of the material to be
examined The surface finish and couplant of the reference
standards shall be acoustically similar to those of the tank and
the couplant therein
10.2.6 Ultrasonic Gauging:
10.2.6.1 The invasive ultrasonic inspection shall make
lo-cated wall thickness measurements of at least 15 % of the
entire tank interior surface area excluding man way entries
The thickness measurements shall be uniformly distributed
over the surface of the tank The invasive ultrasonic inspection
equipment shall be capable of accessing at least 95 % of the
tank interior surface area excluding man way entries and other
tank penetration fittings In areas where corrosion damage is
more severe, as determined by the corrosion technician,
additional measurements shall be made as directed by the
corrosion specialist/cathodic protection specialist so as to
provide a sufficient amount of inspection data to accurately
define the extent of corrosion and to ensure an accurate
leak-free life prediction
10.2.6.2 Depending on surface conditions, the minimum
ultrasonic thickness measurement capability may vary from
0.050 to 0.125 in (1.2 to 3.2 mm) The instrumentation should
be able to measure remaining wall thickness of the tank to an
accuracy of 60.010 in (0.25 mm) and to detect a flat bottom
pit of 0.125-in (3.2-mm) diameter
10.2.6.3 The maximum allowable position error in each
wall thickness measurement position location coordinate is
5 % of the maximum tank dimension
10.2.7 Ultrasonic Test Reports—Record the following data
as a minimum for future reference at the time of each
investigation:
10.2.7.1 Operator’s name and certification level,
10.2.7.2 Instrument description including make, model, and
serial number and setup couplant,
10.2.7.3 Instrument calibration certification including date
performed,
10.2.7.4 Cable type and length,
10.2.7.5 Mode of scanning (manual or automatic),
10.2.7.6 Search unit description, such as, type, size,
frequency, special shoes,
10.2.7.7 Reference standards (and calibration data required
to duplicate the examination), and
10.2.7.8 Location data (coordinates) for thickness
measure-ment data points
10.2.8 Invasive ultrasonic wall thickness measurement may
pose certain safety hazards It is the responsibility of the user
of this guide to establish appropriate safety and health practices
and determine the applicability of regulatory limitations prior
to use
10.3 Data Analysis and Determination of Suitability of a
Tank for Upgrading With Cathodic Protection (RP-0169 and
RP-0187) Using Invasive Ultrasonic Thickness Testing and
Evaluation Including External Site Environment Corrosion
Assessment:
10.3.1 This alternative method includes a mathematical
corrosion prediction model and an analytical report The
analytical report contains the tank, soil chemistry (using Guide
E1323), and inspection data The model is then used to
estimate the leak-free life of the tank using the tank information, ultrasonic thickness measurement test data, and soil chemistry data
10.3.2 Prediction Model:
10.3.2.1 Use a prediction model to determine the probability
of an individual tank leak as a result of corrosion It shall yield the years of leak-free life remaining and the probability of a potential leak of the tank in a specific soil condition The model shall be based on tank inspection data collected and shall include all of the site specific parameters listed in 10.1.3.1 – 10.1.3.5and any test(s) performed in10.1.4 The mathematical formulation used in the prediction model shall be based on accepted physical and electrochemical characteristics of the tank corrosion process
10.3.2.2 Consider the tank suitable for upgrading with cathodic protection if there is:
(a) No measured pitting which perforates the tank wall, (b) Ninety-eight percent of all ultrasonic thickness
mea-surements made on the tank shall be greater than or equal to
50 % of the minimum recommended wall thickness as pro-vided in Underwriters Laboratories Standard UL 58 or the documented original tank wall thickness,
(c) The average metal wall thickness of each 1 m2is greater than 85 % of the original wall thickness, and
(d) The results of the prediction model (for example CERL
N 91/18), as determined by the corrosion specialist/cathodic protection specialist, support that cathodic protection is both reasonable and viable
10.3.3 Inspection Report—This report shall summarize all
tank data collected from the inspection and provide results from the prediction model for each tank including recommen-dations with respect to each tank’s suitability for upgrading using cathodic protection The corrosion specialist/cathodic protection specialist shall be responsible for all data analysis and recommendations
10.4 Cathodic protection can be applied to those tanks which have been evaluated using one of the procedures provided for in Sections 8 and 10 and meet the following criteria
10.4.1 Passes all requirements defined in10.3.2.2 10.4.2 Either a tank tightness test is conducted between three and six months after the tank is cathodically protected, or monthly monitoring with another leak detection system is implemented within one month after the addition of cathodic protection Any leak detection system must meet5.2.2 10.5 A form is included in the Annex A1 which must be utilized to report the results of the authenticated vendor provided information A research report containing examples
of actual authenticated vendor provided information is filed and available from ASTM.9
11 Method C—Invasive Permanently Recorded Visual Inspection and Evaluation Including External Corrosion Assessment
11.1 External Corrosion Assessment Data Gathering:
11.1.1 Conduct the following procedures when assessing the suitability of a steel tank for upgrading with cathodic protection using an invasive method
Trang 711.1.2 Conduct tests by, or as directed by a corrosion
specialist/cathodic protection specialist
11.1.3 Before a tank is suitable for upgrading with cathodic
protection using an invasive approach, the following
site-specific tests shall be conducted for each tank excavation zone
in accordance with industry recognized standard practices:
11.1.3.1 Perform tests as described in9.1.2.1
11.1.3.2 Soil resistivity in accordance with Test Methods
G57 These values shall be measured in the immediate vicinity
of the tank excavation zone and shall, as a minimum, be
measured at depths of 5, 71⁄2, 11, 121⁄2, and 15 ft (1.5, 2.3, 3.5,
and 5 m)
11.1.3.3 Structure to soil potential in accordance with
NACE RP-0285 with at least five such measurements spaced
uniformly about each tank excavation zone
11.1.3.4 Soil pH in accordance with Test MethodG51, soil
chlorides and sulfides in accordance with EPA SW 846 and
Guide E1323 uniformly gathered from three locations about
each tank excavation zone
11.1.3.5 Electrical continuity/isolation in accordance with
NACE RP-0285 of each UST being evaluated
11.1.4 The corrosion specialist/cathodic protection
special-ist should also consider, as a minimum but not be limited to,
performing and evaluating the following tests:
11.1.4.1 Redox potential,
11.1.4.2 Current requirement,
11.1.4.3 Coating resistance,
11.1.4.4 Coating efficiency,
11.1.4.5 Wall thickness,
11.1.4.6 Soluble chloride ion concentration,
11.1.4.7 Sulfide ion concentration,
11.1.4.8 Sulfate ion concentration, and
11.1.4.9 Any other tests deemed necessary
11.2 Field Testing Using Invasive Permanently Recorded
Visual Inspection:
11.2.1 This subsection provides the general procedure for
internally visually inspecting, recording and archieving the
results of the visual inspection of USTs without manned
physical entry into the tanks This information is used in
combination with the data obtained from the external testing
procedures defined in11.1.3to assess the tank’s suitability for
upgrading with cathodic protection
11.2.2 The visual inspection is part of a total assessment
procedure that includes leak detection testing in accordance
with 5.2 and external corrosion evaluation as delineated in
11.1 The recorded documentation (for example, photographic
film, digital or analog tape) is archived and is a permanent
record of the visual inspection
11.2.3 Technical Certification—The person performing this
inspection shall be a corrosion technician The corrosion
specialist/cathodic protection specialist shall conduct an
analy-sis of any suspect corrosion activity that may fail a tank
11.2.4 UST Qualification—The field and laboratory testing
(in accordance with 11.1) is completed either prior to or in
conjunction with performing the internal visual tank
inspec-tion In the event these tests reveal any indication of structural
or electrochemical characteristics that are incompatible with
the effective use of cathodic protection, the tank shall be
considered to have failed the test and the internal visual inspection shall be aborted
11.2.5 UST Preparation—Prior to conducting the internal
visual inspection, the tank must be emptied, cleaned, if necessary, and purged
11.2.6 Emptying Tanks—Tanks to be inspected must be
taken out of operation and all liquid product removed that would otherwise preclude accurate visual inspection of the tank Employ applicable safety precautions and procedures
11.2.7 Purging Tanks—Prior to placing any visual
inspection, recording or lighting apparatus within the fill pipe
or tank, the atmosphere within the tank must be purged to avoid any combustible hydrocarbon/air vapor mixture Purging may
be accomplished by pressure feeding a blanket of carbon dioxide or another inert gas into the tank until sufficient air is displaced to render the interior tank atmosphere safe As an alternative to purging by an inert gas, the tank may be freed of flammable vapor mixtures by air purging
11.2.7.1 All instruments used within the tank, including those used for characterization of the atmosphere, must be certified as intrinsically safe for the appropriate class(es), division(s), and group(s) by a competent authority
11.2.8 Cleaning Tanks—Determined by the corrosion
specialist/cathodic protection specialist upon reviewing the visual record, the tank shall be sufficiently free (clean) of sludge, thick oxides, or other dense residual materials as to allow the internal surface of the tank to be evaluated At least
98 % of the interior surface area of the tank must be visible for inspection
11.2.8.1 If the corrosion specialist/cathodic protection spe-cialist determines the interior surfaces were not adequately clean, the corrosion specialist/cathodic protection specialist shall reject the tank for upgrade with cathodic protection until such time the condition has been corrected and the tank re-evaluated
11.2.9 Lighting Equipment—The in-tank visual recording
system shall be equipped with lighting capable of adequately illuminating the interior steel surfaces so that the defect sizes defined in11.2.10.1can be visually observed and permanently recorded
11.2.10 Visual inspection Resolution:
11.2.10.1 The visual inspection method must identify and permanently record the presence of all detectable pits or corrosion by-products tubercles while observing and perma-nently recording the condition of at least 98 % of the tanks’ interior surfaces
11.2.11 Visual Recording—The minimum resolution of the
visual recording system shall be capable of identifying the location and degree of corrosion activity as listed in11.2.10.1 The system shall also permanently embed the time, structure site, UST location, and date of the visual examination in the visual record It shall also provide for permanently recording the observation comments of the visual inspector
11.2.12 Inspection and Recording—After the tank has been
tested and found to be safe in accordance with11.2.7, and the permanent recording apparatus is in place, the inspection shall
Trang 8be made by a qualified technician working under the
supervi-sion of the responsible corrosupervi-sion specialist/cathodic protection
specialist in accordance with the following minimum
require-ments:
11.2.12.1 Scan all interior tank surfaces to assess the general
inspection conditions and to ensure the tank is sufficiently
clean to permit effective visual inspection
11.2.12.2 At the start of the recording process, record the
date, time, and all necessary tank identification data including
company name and address, project identification number, tank
size, age and identification number, and corrosion technician’s
name
11.2.12.3 Systematically perform and record the visual
corrosion condition on at least 98 % of the internal tank
surfaces
11.2.12.4 Permanently record in the visual record all
perti-nent or unique observations, corrosion activity or damage, and
location relative to the internal tank surface observed by the
corrosion technician
11.2.12.5 Permanently record a summation commentary of
the corrosion technician
11.2.13 Corrosion Activity—The corrosion technician shall
identify any evidence of corrosion including:
11.2.13.1 Perforations—Water intrusion or other visual
evi-dence
11.2.13.2 Rust Tuberculation—Active dark red/maroon
crust
11.2.13.3 Streaks—Elongated in shape, dark red/black in
color at apex
11.2.13.4 Discoloration—Patches showing dark reddish/
black center, becoming lighter toward the edges, usually
irregularly spaced, 3 to 9 in (7.5 to 23 cm) in diameter
11.2.13.5 Pitting—Black in center-bottom of crater, light
red or bright metal near perimeter
11.2.13.6 Scaling or Delaminations—Typical exfoliation,
no discoloration, layered flakes in small 2 to 4-in (5 to 11-cm)
diameter irregular patches
11.2.13.7 Weld Deterioration—Little discoloration, except
possible black/maroon deposit beneath interface; deterioration
of metal within the weld sometimes with cracks and undercuts
11.2.13.8 Cracks—Usually no discoloration, typically near
welds, openings, fittings, connections, and other stress
concen-tration sites
11.2.14 Passive Corrosion Films:
11.2.14.1 General Overall Rust Film—Light red, pink, or
pink/beige; smooth to slightly pockmarked This is not active
corrosion, but an alpha oxide film that is protective or
passivating
11.3 Data Analysis and Report on Determination of
Suit-ability of a Tank for Upgrading with Cathodic Protection
Using Invasive Visual Inspection with External Corrosion
Evaluation:
11.3.1 The examining corrosion technician may record
comments to aid the corrosion specialist/cathodic protection
specialist in evaluation of the tank’s internal surfaces If no
corrosion or deterioration is evident, the report shall so
indicate
11.3.2 The corrosion specialist/cathodic protection special-ist shall be responsible to view the visual permanent record and make a final determination on the suitability of each tank tested for upgrading
11.3.3 After review of the visual permanent record includ-ing all notations and comments, a report shall be prepared and submitted to the UST owner/operator by the corrosion specialist/cathodic protection specialist including the upgrad-ing suitability determination made for each tank This visual record and report shall be kept on file by the UST owner/ operator as part of the required documentation
11.3.4 Any evidence of a perforation or significant corrosion, as defined in accordance with11.2.13, is confirmed
by the corrosion specialist/cathodic protection specialist, or if the corrosion specialist/cathodic protection specialist’s analy-sis of the site corrosion data as defined in11.1and as evaluated
in11.3.5indicates the tank is not a candidate for upgrading by cathodic protection alone Significant evidence of corrosion exists when the corrosion has advanced enough to compromise the integrity and useful life of the tank
11.3.5 Corrosion Data Evaluation Alternatives for Invasive Visual Inspection Procedure:
11.3.5.1 Prediction Model—Use a prediction model to
de-termine the probability of an individual tank leak as a result of corrosion It shall yield the years of leak-free life remaining and the probability of a potential leak of the tank in a specific soil condition The model shall be based on tank inspection data collected and shall include all of the site specific param-eters listed in 11.1.3 – 11.1.3.5 and any test(s) performed in
11.1.4 The mathematical formulation used in the prediction model shall be based on accepted physical and electrochemical characteristics of the tank corrosion process Consider the tank suitable for upgrading with cathodic protection if the results of
the prediction model (for example, CERL N 91/18) ( 3 ), as
determined by the corrosion specialist/cathodic protection specialist, support that cathodic protection is both reasonable and viable or as detailed in 11.3.5.2
11.3.5.2 Site Specific Value Criteria—Corrosion data for
which tanks shall not be considered suitable for upgrade when
a statistical prediction model as defined in11.3.5.1is not used:
(a) Soil resistivity at the average tank depth less than 700
Ω-cm,
(b) Soil pH less than 4.0, (c) Soluble chloride ion concentration greater than 500
ppm,
(d) A positive sulfide test indicating the presence of
sulfate-reducing bacteria in accordance with EPA SW 846
(e) Average tank-to-soil potential on the UST are more
positive than –300 mV with respect to a saturated copper-copper sulfate electrode
11.4 Requirements for applying cathodic protection to tanks which have been tested in accordance with Sections8 and11
and meet the following criteria:
11.4.1 Those tanks that have been tested, found to be leak free, and found acceptable for upgrading in accordance with Sections 8 and 11 and meet the criteria defined in 11.3.4
together with either11.3.5.1or 11.3.5.2, and
Trang 911.4.2 Either a tank tightness test is conducted between
three and six months after the tank is cathodically protected, or
monthly monitoring with another leak detection system is
implemented within one month after the addition of cathodic
protection Any leak detection system must meet5.2.2
11.5 A form is included inAnnex A1which must be utilized
to report the results of the authenticated vendor provided
information A research report containing examples of actual
authenticated vendor provided information is filed and
avail-able from ASTM.9
12 Keywords
12.1 assessment; cathodic protection; corrosion; criteria; EPA; evaluation; inspection; model; prediction; regulation; rust; statistical; steel; suitability; tank; ultrasonic; underground storage tank; upgrade; UST; video; visual
ANNEX (Mandatory Information) A1 THIRD PARTY VERIFICATION
A1.1 SeeFig A1.1
FIG A1.1 Third Party Verification Form
Trang 10REFERENCES (1) Bushman, J., B and Mehalick, T., E “Statistical Analysis of Soil
Characteristics to Predict Mean Time to Corrosion Failure of
Under-ground Metallic Structures,” ASTM STP 1013, ASTM, 1989.
(2) Rogers, W., F “Statistical Prediction of Corrosion Failures,” NACE
International, CORROSION 89, Paper No 596.
(3) Piskin et al, “Leakage Potential of Underground Storage Tanks,” USACERL Technical Report N-91/18, US Army Construction Engi-neering Laboratories, Champaign, IL 61826-9005, June 1991.
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